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Introduction

• If you want to invest in your vehicle's longevity, you need to pay attention to rust, even if there is no rust at the moment.
• In some markets and versions the Jimny is galvanised for additional protection.
  • However, even then they tend to rust, especially if the underbody is not regularly cleaned and minor damages cleaned and sealed.
• If there is rust, it should be remedied before it gets worse.
• If there is no rust, the surfaces it should be preventively protected while it still has not appeared.
• So, scrape and clean the rust from the underbody of the vehicle (if it has rust), and then protect the entire underbody against future rusting with some good anti-rust material.

• An example of a severely corroded Jimny underbody. The vehicle was 10 years old with only 60 000 km on the odometer, mostly on paved, salty alpine roads!
• Suzuki Jimny - body rust - A01.jpg

  This chassis rail is severely weakened

• Suzuki Jimny - body rust - A02.jpg

  This is a critical structural failure, and prevents the vehicle to be licensed for road use

General idea

Areas of Jimny which are most susceptible to rust:

1. Boot / trunk floor
2. Below the rear seats
3. Inner wheel arches
4. Bodywork behind the side plastic mouldings (claddings)
5. Bodywork behind front driving lights

There are several schools of thought regarding which materials and methods should be used to achieve anti-rust protection.

There are generally five types of coatings which are applicable to underbody rust protection:

• Bitumen based (the oldest and cheapest type);
• Synthetic rubber / plastic resin based;
• Waxes;
• Polyurethanes;
• Multi-mix compounds (primer + stiff anti-chipper + paint in one);

Whichever coating type you choose, beware of the following risk factors:

1. It is of paramount importance to eliminate the last atoms of rust from the surfaces which are to be coated.
   • Any remaining rust behind the coating will spread again like cancer, and its advance will even be accelerated because it is concealed and undisturbed.
   • Rust should be first mechanically removed, and then the remaining microscopic traces chemically eliminated.
2. The coating has to be properly applied according to manufacturer's guidelines, and the underlying surface has to be completely clean (and sometimes sanded/roughened for better adhesion).
3. If the above two conditions are not properly met, there is a high risk that the coating will de-laminate or crack in the long term, thus allowing moisture to creep under it.
   • This will severely corrode the underlying metal, as the moisture under it is trapped and never dries off, so the corrosion can thrive under.
   • The worst thing is that this will be invisible to the unsuspecting happy owner.

The perfect rust protection method

Separating body and the frame

• In general, the best results by far can be achieved if the vehicle is first dismantled (body completely separated from the frame).
• However, that is a major undertaking by itself and can be quite an unpredictable process with older vehicles.
  • There will be many seized bolts which break off, some flaky brake lines which crack during removal, some stuck bolts in the bushings will require replacing the bushings, etc.

• The main benefit if the body is separated from the frame (and the transmission and the suspension, which remain on the frame) is that the underside of the body can be thoroughly cleaned and protected, as well as the top of the frame/chassis.
• When the body and the frame are separated, it is then quite convenient and accessible to completely sand blast every square centimeter of the underbody, chassis and all suspension and transmission components.
  • Sand blasting is the most thorough method of removing all rust and most prior coatings.
  • However, sand blasting does not effectively remove prior coating if it is an elastic compound (for example bitumen which is still elastic).
    • The only effective way to remove elastic compounds is to heat them up and manually scrape them off.

Dismantling everything from the frame

• The dismantling of the underbody can be taken further to the "complete/perfect" level by also dismantling all the engine, transmission and suspension elements from the chassis.
• Then the bare chassis (and various suspension elements) can be dipped into a hot zinc bath ("hot zinc plating" process).
  • This is the only method which cleans and protects the inside of the chassis tubes and rails.
  • There is no other solution for the complete chassis protection.
  • Beware that hot zinc plating can be risky, as the chassis might distort due to high temperatures in the bath (something around 450-500 degrees C).
    • Check this with your hot zinc plating facility beforehand!
• Another method is cold zinc plating - dipping the metal into a cold zinc bath and applying electricity throughout (also galled zinc galvanization).
  • This method imposes no risk for the treated parts.
  • However, cold zing plating is thinner and can be applied only to the exterior surfaces of the chassis and other hollow objects, not to the interiors.
• Note that the process of both hod and cold zinc plating usually implies prior dipping of the material to be treated into a pool of special acid, which kills of any remaining rust, dirt, greases and bad spirits.
  • This is usually included in the price of zinc plating, but ask the zing plating facility first!
• Of course, each dismantled suspension piece can also be taken for zinc plating or some other coating.
  • However, the bushes have to be removed first from radius arms, panhard rod arms, anti roll bars, etc.

• After a vehicle component is zinc plated, it can then be treated with a "final" coating.
• There are several materials which can be used.
  • For example: automotive wax, bitumen-alike coating, plastic-alike coating (not recommended for outdoor applications), or polyurethane ("bed-liner") coating, etc.
• It is better to apply some final coatings in two thinner passes (layers) than in one thick pass.
• Opinions on which final coating material is the best vary as much as do opinions on an only proper world religion.

The ordinary rust protection method

General description

• Dismantling half of the vehicle is neither time nor cost effective for most people.
• A standard rust protection method does not involve dismantling of any part of the vehicle.
• Instead, it relies on the principle "do what you can do from underneath".

The disadvantages of the ordinary method are:

• No type of zinc plating can be performed.
  • Pressurized zinc spray cans are (allegedly) much inferior solution to proper zinc plating and they should (allegedly) not be used. It's allegedly better to use a proper primer paint on bare metal.
• Mechanical rust removal techniques (both wire brushes and sand blasting) can not be nearly as thoroughly performed.
  • For example, it is almost impossible to treat the upper surface of the chassis, and access to many "secluded" areas of the underbody is physically restricted, or risky because of brake and fuel lines, vacuum pipes, wires, etc.

"Enhancing" the method

• The limited accessibility issue of the ordinary method can be significantly reduced by undoing all 8 bolts which secure the body to the frame and then slightly temporarily jacking up the body.
  • This is the same procedure as when installing a body lift.
    • It is known that 2" (5 cm) body lifts are trivial to install to a Jimny, as they don't require extending brake lines, vacuum pipes, etc.
  • It has been confirmed that the body can be temporarily jacked up to 4" (10 cm) from the frame just if you disconnect the brake lines from the frame (not from the wheels!).
• Temporarily raising the body by 5-10 cm from the frame gives sufficient access to most hardly accessible areas, like the body above the fuel tank and above the transfer case, top side of the chassis, etc.
• When the body is jacked up, it is easy to access the top of the body-to-chassis bolt mounts, and properly clean them and protect them.
  • These are inaccessible otherwise and tend to rust heavily, and then spread the rust to the rest of the body mounts, which then cause a structural failure of the car!

• The other way to gain access to hardly accessible parts of the body are to remove the fuel tank, the rear exhaust muffler, and/or the transfer case.
  • Removal of the fuel tank will provide much better access to the underside of the body below the rear seats and below the boot.
  • These are the areas which usually suffer the most from rust on Jimnys, and these areas can then be properly cleaned and protected.

Importance of existing rust removal

• Maximum effort should be applied towards the removal of the existing rust.
• Rust is like cancer.
  • If even a tiny untreated bit remains, it will spread again all around in due time, especially if covered with something so it can work undisturbed.
• A standard method of rust removal is by using manual or powered wire brushes (attached to drills, grinders, etc.).
• A much more thorough rust removal can be accomplished only with sand blasting.
• Whichever mechanical rust removal procedure is performed, the treated surfaces should then be "painted" over or sprayed over with some rust treatment (elimination) chemical.
  • Its job is to kill the last tiny thin remains of rust which might have stayed in some pores or scratches after the mechanical removal has been performed.
  • The best chemicals for this job are the ones which chemically alter (transform) the rust into another non-ferrous material (making it impotent).
    • These chemicals are much more expensive than ordinary "rust melting / elimination" chemicals.
    • Prices are usually about 20-40 EUR per liter, but they are well worth it.
    • An example manufacturer of these chemicals is Wurth from Germany.
  • A rust treatment chemical usually needs some time (counted in hours) to do its job.
  • Some of these chemicals require grinding them off after they harden off, while others allow further coating applications like it's a bare metal.
  • Note that these chemicals do not seal the ruface against future rusting!
    • If you don't further treat/coat the surface just after the chemical has done its job, new rust will develop on it soon!

Timing and weather protection

• Note that timing and weather protection is important during the entire rust proofing process.
• For example, if you sand blast a metal surface, and then load it onto a trailer to be taken somewhere else for the next phase, if it's a cloudy day with high humidity (let alone rainy day!), the metal will quickly develop rust flecks on the way to the next station.
• Also, if you wait too long after the application of the rust treatment chemical, the chemical will "evaporate" and the rust will return from the air moisture again ....
• It is also important to obey manufacturer's curing times for each used chemical product.
  • It can be equally bad if you apply something over a a product too early (before it has cured) or too late (after it has completely hardened).
    • In both cases, the next coating might not adhere properly to the first one, creating a significant risk of de-lamination in the long term.

• Most primer paints are porous, meaning that moisture passes through them.
• This means that you need to apply final coating(s) of your choice (which need to be airtight) as soon as the primer paint dries off.
• A lot of people leave the project for a while (maybe to take a rest) after the application of a primer paint, thinking that they have covered the bare metal and how the main "rust shield" is on, but it probably isn't!
• Most primer paints provide no protection against moisture, they are just a "stop-gap" layer so that the final airtight coating can adhere properly!

General procedure of underbody rust proofing

1. Thoroughly check all sections of the underbody, with special attention to factory or additional welds, hidden areas, etc.
   • Pay attention to any sign of existing coating becoming delaminated, cracked or peeled off.
   • Mark around each found problem area so that you do not miss it in the later process.
2. Remove all plugs which seal cavities (like plugs on chassis rails, door sills, etc.)
3. Mechanically remove any rust or peeling/cracked old coatings.
   • Use hand wire brushes, power drill or angle grinder mounted wire brushes, sand blasting, etc.
   • Pay attention not do damage any cables, hoses, wires, etc.
4. Clean and degrease the entire underbody with cleaners/degreasers.
5. Chemically eliminate the last traces of rust on the areas where you mechanically removed rust.
   • Use rust elminating acids or even better rust converter/inhibitor chemicals.
     • Rust converters/inhibitors work on the principle of chemically altering the rust itself, "freezing" it or chemically converting it into another substance.
6. Apply anti-corrosive primer paint on all bare metal surfaces.
   • It is best to use epoxy anti-corrosive primers.
7. On surfaces with existing healthy protective coating, you might need to apply a solvent to "prepare" the surface for further coatings.
   • This depends on the type of existing coating and the type of the anti-chip coating to be applied.
8. Apply seam sealant to all previously rust-treated areas which were welded or where two metal parts/panels join together.
   • It is best to use polyurethane seam sealant.
9. Apply a stonechip coating of your choice (bitumen-based, polyurethane, etc.) to the entire underbody.
   • There are various types of stonechip coatings, with various long-term durability - investigate on your own!
   • It is better to use a spray gun instead of brushes because of less chance of having non-covered micro-spots.
10. Apply wax over the stonechip coating.
    • This is optional, but it provides additional flexible layer of protection, which can self-heal when a rock hits it.
    • It is better to use a spray gun instead of brushes because of less chance of having non-covered micro-spots.
11. Apply wax in all cavities (inside the chassis rails, inside door sills, inside doors, inside anything that is hollow.
    • Use the holes, which you had exposed earlier when removing the plugs, as entry points.
    • Use a spray gun with special long tube with multiple side-facing nozzles on its end.
12. After wax spraying is complete and everything else has dried out, return all plugs into position and seal them with raw rubber.
13. Take a vacation.
    • Preferably in an air spa to clean your lungs of all of the consumed fumes from all these poisons.

Final notes

• Heat up the wax prior to application by putting the bottle in hot water for a while.
  • This will significantly improve the flow of the wax and its spatial placement.
• Use proper protection for eyes, ears (if using power tools), hands and your respiratory system!
• Observe the manufacturers' application guidelines for each used product!
• Check occasionally (at least once a year) for any underbody damages, cracks or delamination of coating.
  • Re-treat the problem area as soon as it is discovered.

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Page last edited on 21/09/2018 by user Bosanek